It is known to provide in wet or dry carpet- or rug-cleaning apparatus, an active element whose function it is to effect a mechanical loosening of soil from the pile, filaments or weave of a carpet and thereby promote removal of soil by a cleaning fluid in a wet-cleaning apparatus or the effect of the air stream in a dry-cleaning apparatus such as a vacuum cleaner.
In wet-cleaning apparatus as well as in dry cleaning apparatus for the removal of soil from carpets and rugs, it is, therefore, common practice to provide a motor-driven device which facilitates the pickup of the soil from the carpet.
For example, the mechanical device can be a rotating brush of any one of a number of types, the bristles of which comb through the pile of the carpet and thereby loosen the soil which normally adheres or is trapped thereby. For example, there are horizontal rotating brushes such as plate brushes and brushes which rotate around vertical axes. Other tools for this purpose are provided without bristles and operate by an impact effect, i.e. as so-called carpet beaters. Such tools generally comprise a rotor or wheel (roller) formed with a bulge or rib which beats against the carpet to loosen the soil thereon.
Beater-type tools of this kind, however, are less efficient than the rotating brushes mentioned previously in the loosening of soil and in providing the soil particles in such form as to enable them to be entrained in the suction air stream.
All of the aforedescribed devices have, however, various disadvantages.
In the case of roller brushes, the bristles sweep through the carpet in only one direction and hence it is necessary to run the carpet-cleaning machine over the rug or carpet in a number of directions. This is to insure that the entire surface of the carpet is thoroughly brushed and that the pile of the carpet is brushed from several directions.
When the carpet-cleaning machine is not displaced in various directions over any particular region, the brush tends to deflect the pile and to engage only the upwardly turned broad surface thereof. Only when the carpet is swept in the opposite direction, do the bristles have the possibility of engaging the opposite side of the pile to release any soil particles which may have been covered over by the deflected pile.
Rotary brushes also have the disadvantage that they have the tendency to untwist long filaments of pule from the carpet and to draw them out of the pile strands.
Another disadvantage of brushes of the aforedescribed type is that contaminants, torn-off filaments or threads and the like tend to accumulate at the roots of the bristles so that the brush, as a whole, tends to grow in size. Unless time-consuming brush cleaning is carried out, the brush is rendered unusable in short order or tends to transfer the soil particles and other material picked up by the brush to the next carpet to be cleaned.
Impact rollers of conventional design have the disadvantage, in addition to the lower efficiency than the brushes, that they tend to flatten the pile of the carpeting and frequently have the same disadvantages as the brushes in that they must be moved across the carpeting in several directions.
It has been attempted to avoid these disadvantages in both wet and dry cleaning machines to provide rapidly operating rollers which have a profile formed by annular projections leaving annular grooves between them.
Such rollers are described for a wet carpet-cleaning apparatus in U.S. Pat. No. 2,407,408, for example, and for a dry carpet-cleaning apparatus in U.S. Pat. No. 2,476,537.
The carpet-working roller of the last-mentioned patent comprises inclined elliptical rings which, because of their inclined orientation on the inner member of the roller, have a circular axial profile, i.e. viewed along the axis of the roller, the projections are seen to have a circular outline.
The inclined orientation of these annular disks has the effect that at each region of the carpet swept by each disk, for every rotation of the roller, the pile is displaced axially to one side and then to the opposite side.
This lateral back and forth movement occurs as the roller is displaced transverse to its axis along the carpet. As a result, the soil trapped in the pile and between the strands of the pile is loosened readily and the pile is never bent over to the point that portions of the pile remain unswept by the projections.
Investigations have shown, however, that the rollers of this construction are not completely effective because they consist of elastically deformable material. These investigations have demonstrated, moreover, that the use of a yieldable material has the tendency to limit the back and forth movement of the pile. The elastic material was chosen to prevent damage to the carpet but, in fact, had the effect of reducing the soil-loosening efficiency of the device.
Indeed, because the elastically yieldable material is itself bent back and forth by a resistance of the pile upon rotation of the roller, the annular disks develop residual necks, bends and edges which sharply increase the wear of the roller and the tendency to damage the carpet by seizing filaments of the pile. In many cases, moreover, the material is so yieldable and the pile so dense that the yieldable material of the profiled roller does not penetrate sufficiently deeply between the fibers of the carpet to effect a back and forth oscillation thereof.
Lateral forces upon the roller are also not completely transferred to the carpeting as a result the annular profiles, because of their yieldability, take up, to a large measure, these lateral forces.
Apparently, this was recognized in the development of the aforedescribed prior art roller since, in the last-mentioned patent, there is described a system for compensating for the lateral forces. To this end, half of the roller is provided with annular disk projections which are inclined in one direction while the other half of the roller has inclined disk projections oriented in the opposite direction.
This construction has been found to have the disadvantage that, in the center of the roller, no annular disk projections can be provided and hence a central strip of the carpet swept by the roller remains unagitated thereby. In practice, therefore, this profiled roller has not received widespread acceptance in the carpet-cleaning art.